See Wikipedia . Drugs known to be ?–agonists include cocaine, morphine/diacetylmorphine, opipramol, pcp, fluvoxamine, methamphetamine, dextromethorphan, and the herbal antidepressant berberine. However the exact role of ?–receptors is difficult to establish as many ?–agonists also bind to other targets such as the ?-opioid receptor and the nmda receptor.Recently selective ?–receptor agonists were shown to produceantidepressant effects in mice. Best wishes.